Choke vacuum break unit

ABSTRACT

A carburetor choke vacuum break unit has a check valve which restricts flow out of the unit to provide a period of delay between the application of manifold vacuum to the unit and the opening of the choke by the unit. To prevent plugging of the check valve, a purge hole is provided between the check valve and the source of vacuum; this permits a continuous flow of air into the vacuum conduit to prevent pulsations in manifold vacuum from transmitting foreign matter to the unit where it could tend to plug the check valve.

United States Patent 1 Taylor CHOKE VACUUM BREAK UNIT [75] Inventor: Roland S. Taylor, N.Y.

[73] Assignee: General Motors Corporation,

Detroit, Mich.

[22] Filed: Sept. 12, 1972 [21] Appl. No.: 288,403

[52] US. Cl. 123/119 F, 261/39 B [51] Int. Cl. F02m 1/10, F02m 1/08 [58] Field of Search 261/39 R, 39 B;

[56] References Cited UNITED STATES PATENTS 2/1955 Carlson 123/119 F 12/1957 Eickmeier 123/119 F l/l961 Braun 123/119 F Nov. 20, 1973 6/1965 Ball 261/39 B 9/1966 Lucas et al 261/39 B Primary Examiner-Wendell E. Burns AttorneyJ. L. Carpenter et al.

[5 7 ABSTRACT A carburetor choke vacuum break unit has a check valve which restricts flow out of the unit to provide a period of delay between the application of manifold vacuum to the unit and the opening of the choke by the unit. To prevent plugging of the check valve, a purge hole is provided between the check valve and the source of vacuum; this permits a continuous flow of air into the vacuum conduit to prevent pulsations in manifold vacuum from transmitting foreign matter to the unit where it could tend to plug the check valve.

2 Claims, 3 Drawing Figures CHOKE VACUUM BREAK UNIT This invention relates to carburetor choke vacuum break units.

Some recent choke vacuum break units have included a check valve which restricts flow out of the vacuum break unit to provide a time delay between the application of manifold vacuum to the unit and the opening of the choke by the unit. This check valve has a small opening which, under certain conditions of operation, is susceptible to plugging if fluctuations in manifold vacuum transmit foreign matter to the vacuum break unit and cause a deposit on the check valve.

This invention provides a purge hole in the vacuum fitting, between the check valve and the source of vacuum, which permits a flow of filtered air into the vacuum line. A decrease in manifold vacuum, which formerly could cause a flow of air and fuel from the intake manifold to the vacuum break unit, now results in a reduction in air flow from the purge hole to the manifold together with a flow of filtered air from the purge hole past the check valve into the vacuum break unit. This construction prevents foreign matter from reaching the check valve and thus prevents plugging of the check valve.

The details as well as other objects and advantages of this invention are set forth in the remainder of the specification and are shown in the drawing in which:

FIG. 1 is a side elevational view of a carburetor equipped with this vacuum break unit;

FIG. 2 is an enlarged sectional view of this vacuum break unit showing the details of its internal construction; and

FIG. 3 is a view of a portion of the vacuum break unit, further enlarged to show the details of the check valve.

Referring first to FIG. 1, the carburetor has a mixture conduit 12 in which choke and throttle valves 14 and 16 are disposed. Choke valve 14 is mounted on a shaft 18, and a lever 20 is secured to shaft 18. A link 22 connected to lever 20 extends to a thermostat 24. Upon an increase in temperature, thermostat 24 permits downward movement of link 22 and clockwise, choke opening, rotation of lever 20, shaft 18, and choke valve 14.

A bracket 26 supports a vacuum break unit 28 on carburetor 10. As shown in FIG. 2, vacuum break unit 28 includes rear and front cover members 30 and 32. Front cover 32 is formed about a bracket adapter 34 for receiving bracket 26, and'rear cover 30 has a tubular fitting 36 formed therein.

A diaphragm 38 is clamped between front and rear cover members 30 and 32 and carries front and rear washer members 40 and 42. Front washer 40 is crimped over a stem guide 44 which surrounds the stem 46. A spring 48 biases stem 46 against washer 40.

A slot 50 in stem 46 is adapted to receive a link 52 which, as shown in FIG. 1, extends to choke lever 20.

As also shown in FIG. 1, a hose 54 extends from fitting 36 to a fitting 56 of carburetor 10 which extends from a passage 58 sensing manifold vacuum in mixture conduit 12 below throttle 16.

In operation, manifold vacuum applied through fitting 36 to vacuum unit 28 displaces diaphragm 38 leftwardly against the bias of a spring 60. Diaphragm 38 carries stem guide 44 leftwardly compressing spring 48 to bias stem 46 and link 52 leftwardly and chock lever 20, choke shaft 18 and choke valve 14 in a clockwise, choke opening, direction.

As shown in enlarged detail in FIG. 3, a check valve unit 62 has a protrusion 64 received in tubular fitting 36. Protrusion 64 is formed as a portion of a soft brass valve retainer 66 which defines a passage 68 from fitting 36 into the chamber 70 defined between rear cover member and diaphragm 38. A shoulder 72 in retainer 66 receives a paper filter element 74 and a soft brass valve seat member 76. The right-hand surface 78 of seat member 76 defines a flat annular valve seat which receives a fluorosilicone O-ring 80. A soft brass valve disk 82 is received against the other side of O-ring 80 and is biased thereagainst by the central finger 84 of an otherwise annular Mylar disk 86. The rim 88 of disk 86 is retained by the rim 90 of retainer 66. A paper filter element 92 covers the open end of valve unit 62 and is retained in place by a valve cap 94 which also acts as a seat for spring 60.

In operation, upon an increase in manifold pressure, valve disk 82 is displaced from O-ring 80 against the bias of finger 84 to permit unrestricted flow into chamber 70. Upon a decrease in manifold pressure, finger 84 forces valve disk 82 against O-ring 80, and flow from chamber 70 is restricted to pass through a notch 96 coined'in the face 97 of valve disk 82 received against O-ring 80.

' manifold vacuum. An epichlorhydrin housing 100 is mounted on fitting 36 and contains a'felt filter element 102 therein.

In operation, a continuous flow of air is drawn through the annular opening 104 between housing 100 and rear cover member 30, through filter element 102, and through opening 98 into fitting 36. A decrease in manifold vacuum (an increase in manifold pressure) would normally result in a pulsation of air and fuel from mixture conduit 12 through passage 58, fitting 56, hose 54, fitting 36, and passage 68 in check valve unit 62 to chamber 70, but this does not occur when opening 98 is provided. Instead, the continuous flow of air into fitting 36 through opening 98 is reduced, and the pressure in chamber 70 is permitted to increase by filtered air flow from opening 98 through passage 68 and check valve unit 62. This prevents foreign matter from depositing on valve disk 82 which could plug notch 96.

In a practical embodiment of this invention, notch 96 has a dimension of 0.004 inches, filters 74 and 92 screen particles larger than 10 microns, and opening 98 provides a flow of from 400 to 800 cc of air per minute at a manifold vacuum of 18 inches I-Ig.

I claim:

1. For use on an internal combustion engine carburetor having a choke, a vacuum break unit for opening said choke and comprising a cover member closed by a diaphragm to form a chamber, a stem extending from said diaphragm and adapted for connection to said choke for positioning said choke in accordance with the position of said diaphragm, spring means biasing said diaphragm away from said cover member, a tubular fitting extending from said cover member and adapted for connection to a source of vacuum for applying vacuum to said chamber, a valve associated with said fitting for controlling flow between said fitting and said chamber, said fitting having an opening to atmosphere disposed between said valve and said source of vacuum to provide a continuous flow of air into said fitting whereby a pressure increase insaid source of vacuum results in a reduction in air flow from said opening to said source and-1g a flow of air from said opening to said chamber and is prevented from resulting in How from said source to said chamber to thereby prevent material in said source from encountering said valve, and air filter means disposed over said opening.

2. The vacuum break unit of claim 1 wherein said valve comprises a retainer supported in said fitting and defining a passage from said fitting to said chamber, an annular flat valve seat disposed about said passage, an

O-ring received on said valve seat, a flat valve disk received on said O-ring, and spring means biasing said valve disk against said O-ring whereby air flow from said opening to said chamber may displace said valve member from said O-ring against the bias of said spring means resulting in unrestricted air flow through said passage to said chamber, said valve disk having a notch coined therein adjacent said O-ring whereby flow from said chamber through said passage is restricted to flow through said notch between said valve disk and said O- ring. 

1. For use on an internal combustion engine carburetor having a choke, a vacuum break unit for opening said choke and comprising a cover member closed by a diaphragm to form a chamber, a stem extending from said diaphragm and adapted for connection to said choke for positioning said choke in accordance with the position of said diaphragm, spring means biasing said diaphragm away from said cover member, a tubular fitting extending from said cover member and adapted for connection to a source of vacuum for applying vacuum to said chamber, a valve associated with said fitting for controlling flow between said fitting and said chamber, said fitting having an opening to atmosphere disposed between said valve and said source of vacuum to provide a continuous flow of air into said fitting whereby a pressure increase in said source of vacuum results in a reduction in air flow from said opening to said source and in a flow of air from saiD opening to said chamber and is prevented from resulting in flow from said source to said chamber to thereby prevent material in said source from encountering said valve, and air filter means disposed over said opening.
 2. The vacuum break unit of claim 1 wherein said valve comprises a retainer supported in said fitting and defining a passage from said fitting to said chamber, an annular flat valve seat disposed about said passage, an O-ring received on said valve seat, a flat valve disk received on said O-ring, and spring means biasing said valve disk against said O-ring whereby air flow from said opening to said chamber may displace said valve member from said O-ring against the bias of said spring means resulting in unrestricted air flow through said passage to said chamber, said valve disk having a notch coined therein adjacent said O-ring whereby flow from said chamber through said passage is restricted to flow through said notch between said valve disk and said O-ring. 